How to add hydrological boundary data to a 2D model

Hydrological boundaries can provide boundary inflow data to either a 1D or 2D model. They utilise hydrological parameters and rainfall-runoff processes to produce inflow hydrographs in a format compatible with your model. Flood Modeller includes a number of different boundaries, each one incorporates a different rainfall-runoff calculation method. These are as follows:

• FEH - Rainfall-runoff model based on procedures described in the UK Flood Estimation Handbook (1999)
• ReFH - Revitalised flood hydrograph method derives an inflow hydrograph for a catchment or sub-catchment.
• FRQSIM - Derives an inflow hydrograph from a catchment or subcatchment using FRQSIM (an abbreviation of 'flood FReQuency SIMulation'), a bespoke, fully distributed rainfall-runoff method
• FSSR16 - Rainfall-runoff model based on procedures set out in the Flood Studies Report (1975) and includes revisions contained in subsequent supplementary reports
• Rainfall/evaporation – Boundary provides inputs of any combination of rainfall, evaporation and infiltration applied over a specified area (to convert depth values into inflow volumes).
• Generic rainfall-runoff - Allows complete freedom for the user to select different model components to be integrated within the same hydrological boundary unit. Currently, the models implemented to date focus on the globally-applicable SCS (US Soil Conservation Service) model, the Green-Ampt loss model (an observed rainfall model) and simple constant and recession baseflow models.

Further technical information on these methods can be found in the technical reference section of the user guide (Hydrological Boundaries).

This section details the procedure for adding these node types to your 2D models.

Hydrology data for a 2D model can consist of one or more boundary inputs of rainfall or infiltration data applied over a user defined area (within your 2D domain). Note that evapotranspiration or groundwater infiltration inputs will be negative, i.e. drawing water from your flood flows. These hydrology data are optional for a 2D model and do not have to be specified (provided you include some other form of input boundary, e.g. flood depth, flow time series or linked 1D model)

To define hydrological boundaries in a 2D model:

1. Load the 2D model simulation file (xml file) you wish to work on into the project view and make it the active simulation by highlighting in the project view (click on the filename in the project view). Alternatively, if you are starting a new 2D simulation, right-click on the simulations section of the project view and select new 2D simulation from the displayed menu to specify a simulation name and save location.
2. Access the 2D simulation window by double-clicking on the appropriate simulation name in the project view (or right-click on the simulation name and select Open from the displayed menu).
3. Select the Domains tab and then the Rainfall/Infiltration sub-tab. From here, you can drag your shapefile representing the area over which the rainfall/infiltration will be applied from the Layers panel to this window. 
4. A new window is displayed prompting you to define the details of the new boundary data source, as shown below.
   The following options are provided to define the hydrological time series associated to the shapefile:
   • Use Hydrology Unit File - You can utilise the 1D hydrology tools to define hydrology nodes in a new (empty) network and then save these data as a separate event (.ied) or network (.dat) file. This can then be associated to your 2D boundary shapefile. If you select this option, use the button to the right of the field to browse to the relevant file.
   • Use Timeseries File - You can associate a timeseries data file to your hydrological boundary. This must be a comma separated variable (.csv) format. Data in a csv file must be prepared with dates (or dates and times) and rainfall values in two adjacent columns. If you select this option, use the button to the right of the field to browse to the relevant file. You will notice two drop-down fields below become enabled - you must select the Time Units (hours by default) and Rainfall Units (mm by default) from these. 
   • User Entered  - This option enables the table provided on the right side of the window, in which you can manually type your timeseries data. You will notice two drop-down fields below also become enabled - you must select the Time Units (hours by default) and Rainfall Units(mm by default) from these. 
     Note

     The option is provided to cut and paste data into the hydrology timeseries table from a spreadsheet, e.g. MS Excel. This data must be prepared with dates (or dates and times) and rainfall values in two adjacent columns. The right-click menu from this table provides a variety of options you may find helpful.
5. By default, boundary data added will be as Rainfall Only. You can select to instead introduce a spatial loss component for your hydrological input, using the Green & Ampt method. To do this, click the Rainfall and Spatial Loss radio button, and provide a loss shapefile, together with the Green & Ampt parameters (either via a look-up file, or by filling in the user-entered look-up table provided at the bottom of the window). Full details of this method are provided within the technical reference, on the 2D Simulations - Rainfall / Infiltration Sub-tab page.
   If you select the Use Hydrology Unit File option to provide your data, you further have the option to apply Rainfall and Lumped Loss, taking the "rainfall" values after infiltration has been applied by the hydrology unit. In the case where your hydrology unit is the Generic Rainfall/Runoff unit, you can apply Rainfall and Spatial Loss via the curve number (CN) method as an alternative to the Green & Ampt method. Full details of these methods are also provided within the technical reference, on the 2D Simulations - Rainfall / Infiltration Sub-tab page. 
6. After adding a hydrological boundary to your simulation, it will appear listed as a hydrology source on the 2D simulation window. You can further edit any property of an existing boundary in this table. Click on the cell to be edited and you will be able to either browse to a different file or select a different option from the provided dropdown list (edit option depends on the cell selected). If you have specified a manually entered timeseries, then you can edit any value in the right-hand table by clicking on the cell and typing in a new value.
7. You can specify multiple hydrology input areas, i.e. separate polygon shapefiles. However, each one must be defined as a separate item associated to separate timeseries datasets.
8. When you have defined all required hydrological data sources for your 2D simulation, click the Save button on the main 2D simulation window to ensure all changes are stored.